Assessment of the relative dose distribution around an  line source using a liquid ionization chamber

Bahar-Gogani, Jalil; Wickman, G.; Johansson, Lennart; Johansson, Bengt

doi:10.1118/1.598698

Cited by 10 publications

(8 citation statements)

References 23 publications

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“…There have been a number of studies on the dosimetry of brachytherapy experiments involving the use of ion chambers (Bahar-Gogani et al 1999, Mishra et al 1997, Tolli and Johansson 1993 and thermoluminescent dosimeters (TLDs) (Anctil et al 1998, Muller-Runkel andCho 1994). In all these studies, however, the radial distance from the source centre to the measurement points has been larger than 10 mm.…”

Section: Introductionmentioning

confidence: 99%

The effect of water molecular self-diffusion on quantitative high-resolution MRI polymer gel dosimetry

et al. 2003

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In polymer gel dosimetry, magnetic resonance imaging (MRI) is used to determine the spin-spin relaxation rate (R2) which in turn can be correlated with absorbed dose to provide a map of the spatial distribution of the absorbed dose in the irradiated dosimeter. High accuracy, precision and reproducibility of these dose maps are essential. Moreover, for dose verification around brachytherapy sources used for intravascular brachytherapy, a high spatial resolution is required (typically 0.01-0.1 mm). To achieve these microscopic resolutions, strong imaging gradients are applied. The Brownian motion of water molecules in the presence of these strong magnetic field gradients causes an attenuation of the MR signal. When using a multiple spin-echo sequence, this may result in a significant deviation in the measured R2. The diffusion-related change in R2 at high resolutions was investigated experimentally and correlated with predictions that were obtained numerically and algebraically. Diffusion weighting is determined by the self-diffusion coefficient D, and imaging parameters, quantified by the b-factor. The b-factor was calculated for a multiple spin-echo sequence for different gradient strengths and gradient pulse durations. The variations in R2 that were observed when changing the matrix size and slice thickness are explained. It is shown that a linear correlation between the matrix size and the variation in R2 is based on the diffusion weighting caused by the read-out gradients and slice selective gradients. In conclusion, the essence of taking into account molecular self-diffusion to quantify variations in the measured dose-R2 response when using high-resolution MRI in polymer gel dosimetry is emphasized.

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Section: Introductionmentioning

confidence: 99%

The effect of water molecular self-diffusion on quantitative high-resolution MRI polymer gel dosimetry

et al. 2003

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“…[19][20][21] In Ref. 16, absorbed dose distributions calculated with GEANT for 192 Ir wires have been compared with measurements done with a liquid ionization chamber, obtaining a good agreement.…”

Section: Monte Carlo Simulation Codementioning

confidence: 92%

“…13 Furthermore, the applicability of the GEANT code to 192 Ir energies has been checked and described in previous papers by our group 14,15 and has been tested experimentally by other authors. 16 In Ref. 14 the results obtained with GEANT were compared to those obtained by Williamson 17 for the same sources, for which Monte Carlo calculations 18 have been widely theoretically and experimentally tested for all the gamma energies used in brachytherapy.…”

Section: Monte Carlo Simulation Codementioning

confidence: 99%

A Monte Carlo investigation of the dosimetric characteristics of the CSM11 137Cs source from CIS

et al. 2000

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The purpose of this study is to calculate basic dosimetry data for a CSM11 low dose rate 137Cs source in water. This source is widely used in afterloadable dome cylinders designed to homogeneously irradiate the vaginal cuff alone or additional areas of the vagina in hysterectomized patients. In this study, the Monte Carlo simulation code GEANT, incorporating in detail source geometry, is used to investigate the dosimetric characteristics of the source. The calculated data were analyzed using a fitting procedure that is described in detail. Absolute dose rate distributions in water were calculated around this source and are presented as conventional 2D Cartesian lookup tables (classically along-away tables). Also, the dose calculation formalism endorsed by the Interstitial Collaborative Working Group and the AAPM Task Group 43 have been calculated. The calculated dose rate constant for this source is lambda = 1.096 +/- 0.002 cGy h(-1) U(-1). The anisotropy function results in about 50% deviations from isotropy at positions near the long axis of the source. The radial dose function is given as a polynomial that reproduces the calculated data up to 20 cm. Best-fit values of attenuation coefficients suitable for use in Sievert integral calculations have been derived.

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“…This source model has been widely studied in the literature using analytically derived Sievert 2 algorithms, experimental methods and Monte Carlo ͑MC͒ calculations. [3][4][5][6][7][8][9] Presently, the commercially available treatment planning systems approximate the dose rate distribution of the wires or elongated sources applying the superposition principle using one of the following methods:…”

Section: Introductionmentioning

confidence: 99%

Dosimetric characterization of Ir‐192 LDR elongated sources

Laarse¹,

Granero²,

Pérez‐Calatayud³

et al. 2008

Medical Physics

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Ir-192 wires have been used in low-dose-rate brachytherapy for many years. Commercially available treatment planning systems approximate the dose rate distribution of the straight or curved wires applying the superposition principle using one of the following methods: (i) The wire is modeled as a set of point sources, (ii) the wire is modeled as a set of small straight segment wires, (iii) the values of the parameters and functions of the American Association of Physicists in Medicine (AAPM) Task Group 43 protocol are obtained for wire lengths between 3 and 7 cm assuming some simplifications. The dose rate distributions obtained using these methods for linear wires of different lengths and U-shaped wires present significant deviations compared to those obtained by Monte Carlo. In the present study we propose a new method to model 192Ir wires of any length and shape, named the Two Lengths based Segmented method. This method uses the formalism stated in the AAPM Task Group 43 protocol for two straight wires only, 0.5 and 1 cm, to obtain the dose rate distribution around wires of any length (down to 0.3 cm and up to 10 cm) improving on the results of the aforementioned ones. This method can easily be applied to dose calculations around other wires, such as Pd-103 ones.

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Assessment of the relative dose distribution around an line source using a liquid ionization chamber

Cited by 10 publications

References 23 publications

The effect of water molecular self-diffusion on quantitative high-resolution MRI polymer gel dosimetry

The effect of water molecular self-diffusion on quantitative high-resolution MRI polymer gel dosimetry

A Monte Carlo investigation of the dosimetric characteristics of the CSM11 137Cs source from CIS

Dosimetric characterization of Ir‐192 LDR elongated sources

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